Density and strength distribution in the human subchondral bone plate of the patella

Purpose: The aim of this study was to map the strength distribution of the human patella and correlate it to the subchondral bone plate density obtained by means of computed tomographyosteoabsorptiometry (CT-OAM). Methods: Measurements were performed at 34 standardized points on each patella. The mineralization patterns of the subchondral bone plate of 20 patellae were displayed with the help of CT-OAM. False-coloured distribution patterns for our measurements were generated. The mechanical strength was determined at the same points by indentation testing. Results: We showed that neither the density nor the mechanical strength is distributed homogeneously but exhibited regular, reproducible distribution patterns which mirror long-term stress distribution in articular surfaces. A direct correlation was found between both parameters in the subchondral bone plate. Conclusion: The correlation of density and mechanical strength makes CT-OAM a valuable tool to assess and monitor changes in the strength of the subchondral bone plate in viv

The subtalar and talonavicular joints: a way to access the long-term load intake using conventional CT-data

Purpose: The aim of this study was to investigate the distribution of density of the subchondral bone plate within the articular surfaces of the subtalar and talonavicular joint regarding to its mineralisation and to verify whether a correlation to the mechanical bone strength exists. Methods: A total of 21 cadaverous lower leg specimens were investigated. Computed tomography osteo-absorptiometry (CT-OAM) was used to display the mineralisation of the subchondral bone plate analysing its density. The mechanical strength was measured by means of indentation testing. The distribution pattern was analysed regarding their dissemination with the main focus on number and location of their maxima. The correlation of both parameters was evaluated by linear regression. Results: The mineralisation and the mechanical strength were not distributed homogenously throughout the articular surfaces but showed unique and reproducible patterns. The range of absolute values for density and strength varied in between the samples and joint surfaces, but the number and location of the maxima evaluated by both methods showed to be concurring. The coefficient of correlation of both datasets ranged from 0.76 to 0.95 (median 0.88) and showed a linear dependency. Conclusions: Density distribution and mechanical strength of the subchondral bone plate are significantly associated and can be seen as a mirror of the long-term load intake of a joint. It can be concluded that CT-OAM as a tool to visualize subchondral bone plate density distribution regarding to its mineralisation can be used to indirectly gain information about joint biomechanics in vivo by the use of conventional CT-data

Thickness distribution of the glenohumeral joint cartilage: a quantitative study using computed tomography

Purpose: Among late signs like sclerosis, cysts and osteophytes, alteration of cartilage is a common problem in osteoarthritis. To detect abnormal states in the glenohumeral joint, the physiologic distribution of the cartilage thickness must be known, which will allow physicians to better advise patients. High-resolution computed tomography (CT) data in soft tissue kernel provide highly accurate quantitative results and are a useful method to determine the geometrical situation of the glenohumeral joint. The objective of this study was to characterize the distribution of the thickness of the glenohumeral joint cartilage using CT. Methods: To investigate the distribution of thickness of the joint cartilage, CT images in soft tissue kernel of nine specimens were analyzed using image visualization software. Statistical analysis of the obtained data was performed using the ANOVA test. Results: Results showed different patterns in the glenoid cavity than in humeral head. Cartilage thickness in all glenoids showed maxima in the inferior and anterior portion, whereas central areas are covered with the thinnest cartilage layer. Maximum cartilage thickness in the humeral head was found in the central and superior parts. Conclusion: We could show that the distribution of cartilage thickness in the glenohumeral joint is not homogenous and that there exist several reproducible patterns. Evaluation of cartilage thickness in the glenohumeral joint is of high interest in basic and clinical research

Insight into the 3D-trabecular architecture of the human patella

The subchondral bone plate (SBP), a dynamic component of the osteochondral unit, shows functional adaptation to long-term loading by distribution of the mineral content in a manner best serving the mechanical demands. Since the received joint-load is transmitted into the trabecular system, the spongy bone also exhibits differences in strain energy density which models it for optimal support. To evaluate the regional variations in trabecular architecture, in accordance with the density distribution of the SBP revealing its long-term load intake, CT- and muCT-datasets of ten physiologic patellae were analysed for defined parameters of bony structure. For the SBP, the density distributions as well as area measurements were used. The trabecular architecture was described using parameters of bone morphology comprising the first 5mm (examined in 1mm steps) below the SBP. The obtained measurements are: Bone volume fraction (BV/TV); Bone surface density (BS/TV); Trabecular number (Tb.N); Trabecular separation (Tb.Sp); Trabecular thickness (Tb.Th); structure model index (SMI); and the Degree of anisotropy (DA). The evaluated architectural parameters varied within the trabecular system and showed an inhomogeneous distribution pattern. It proved to be distinctive with maxima of material and stability situated below areas of the highest long-term load intake. With increasing depth, the pattern of distribution was persistent but lessened in intensity. The parameters significantly correlated with the density distribution of the SBP within the first and second millimetres. With increasing depth down to the fifth millimetre, the coefficients of correlation decreased for all values. The trabecular network adapts to its mechanical needs and is therefore not homogenously built. Dependent upon the long-term load intake, the trabecular model optimizes the support with significant correlation to the density distribution of the SBP

Osteoarthritis alters the patellar bones subchondral trabecular architecture

Following the principles of "morphology reveals biomechanics," the cartilage-osseous interface and the trabecular network show defined adaptation in response to physiological loading. In the case of a compromised relationship, the ability to support the load diminishes and the onset of osteoarthritis (OA) may arise. To describe and quantify the changes within the subchondral bone plate (SBP) and trabecular architecture, 10 human OA patellae were investigated by CT and micro-CT. The results are presented in comparison to a previously published dataset of 10 non-OA patellae which were evaluated in the same manner. The analyzed OA samples showed no distinctive mineralization pattern in regards to the physiological biomechanics, but a highly irregular disseminated distribution. In addition, no regularity in bone distribution and architecture across the trabecular network was found. We observed a decrease of material as the bone volume and trabecular thickness/number were significantly reduced. In comparison to non-OA samples, greatest differences for all parameters were found within the first mm of trabecular bone. The differences decreased toward the fifth mm in a logarithmic manner. The interpretation of the logarithmic relation leads to the conclusion that the main impact of OA on bony structures is located beneath the SBP and lessens with depth. In addition to the clear difference in material with approximately 12% less bone volume in the first mm in OA patellae, the architectural arrangement is more rod-like and isotropic, accounting for an architectural decrease in stability and support. (c) 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

Comparison of knee joint orientation in clinically versus biomechanically aligned computed tomography coordinate system

Background: Preoperative planning of total knee arthroplasty is usually performed using knee-centred computed tomography (CT) data sets. The disadvantage of these data sets is having no account of the biomechanical axis of the lower extremity, known as Mikulicz line. It aligns the femoral head to the middle of the talocrural joint. For optimal prosthesis arrangement, the knee CT data set must therefore be brought in congruency with this line of loading to achieve the best results and eliminate rotational malalignments.This study aims to establish a relation between the knee-centred clinical coordinate system (CCS) and a biomechanical coordinate system (BCS) based on the Mikulicz line. Methods: CT data sets of 45 lower extremities were evaluated. Using VG Studio Max, a visualisation and measurement software program; each CT data set was aligned according to the CCS and BCS. After superimposing both the aligned data sets, the deviations of both coordinate systems in all three planes were measured with the centre of the knee defined as the origin. Results: For the coronal plane, the CCS was demonstrated to be 2.54° in adduction compared to the BCS [standard deviation (SD) = 1.8°]. In sagittal view, the CCS was demonstrated to be 0.3° retroversed (SD = 3.27°). Finally, the deviation in the axial plane showed an outward rotation of 3.39° (SD = 1.99°). The alignment as well as the measurements demonstrated high intraobserver and interobserver reproducibility. Conclusion: Both coordinate systems can be established in knee-centred CT data sets in a reproducible manner. Clearly, the CCS differs significantly from the BCS describing the biomechanical axis, but mathematical-based adaptations and corrections can be performed. The translational potential of this article: The findings of this study allow a mathematical conversion of a knee CT to the biomechanical axis of the leg. Keywords: Alignment, Computed tomography, Coordinate system, Mikulicz line, Total knee arthroplast

Mineral density and penetration strength of the subchondral bone plate of the talar dome : high correlation and specific distribution patterns

The subchondral bone plate plays an important role in stabilizing the osteochondral joint unit and in the pathomechanism of osteochondral lesions and osteoarthritis. The objective of the present study was to measure the mineral density distribution and subchondral bone plate penetration strength of the talar dome joint facet to display and compare the specific distribution patterns. Ten cadaver specimens were used for computed tomography (CT) scans, from which densitograms were derived using CT-osteoabsorptiometry, and for mechanical indentation testing from which the penetration strength was obtained. Our results showed 2 different distribution patterns for mineral density and penetration strength. Of the 10 specimens, 6 (60%) showed bicentric maxima (anteromedially and anterolaterally), and 4 (40%) showed a monocentric maximum (either anteromedially or anterolaterally). A highly significant correlation (p > .0001) for both methods confirmed that the mineral density relied on local load characteristics. In conclusion, the biomechanical properties of the subchondral bone plate of the talar dome joint facet showed specific distribution patterns. CT-osteoabsorptiometry is a reliable method to display the mineral density distribution noninvasively. We recommend CT-osteoabsorptiometry for noninvasive analysis of the biomechanical properties of the subchondral bone plate in osteochondral joint reconstruction and the prevention and treatment of osteoarthritis and osteochondral lesions

Functional and Structural Details about the Fabella: What the Important Stabilizer Looks Like in the Central European Population

The posterolateral corner of the knee accommodating the fabella complex is of importance in orthopaedic surgery. Unfortunately, there is a lack of data in literature for clinical routine. Therefore, we investigated the fabella's characteristics, biomechanical nature, and present histologic details. Of special interest were the fabella's occurrence and position, calcium concentration as long-term load intake indicator, and the histology. Within our analysis, fabellae were found in 30.0% of all datasets, located on the upper part of the posterolateral femoral condyle. The region of fabella contact on this condyle showed a significantly lower calcium concentration than its surroundings. Histologically, the fabella showed no articular cartilage but a clearly distinguishable fabellofibular ligament that consisted of two bundles: one, as already described in literature inserted at the fibular tip, and another part newly described on the top of the lateral meniscus. In its role of stabilizing the soft tissue structures of the posterolateral knee, the fabella seems to serve as suspension for the ligaments evolving from its base. Even though a joint formation of any kind is unlikely, the presence of a fabella needs to be kept in mind during knee examination and any surgical procedures

The glenohumeral joint - a mismatching system? A morphological analysis of the cartilaginous and osseous curvature of the humeral head and the glenoid cavity

BACKGROUND: Radial mismatch, glenohumeral conformity ratios and differences between cartilaginous and osseous radii highly depend on the measured plane. The comparison of cartilaginous radii between humeral head and glenoid in different planes provides new information to understand the degree of conformity during abduction of the upper limb. METHODS: To investigate the radii, CT-images in soft-tissue kernel of 9 specimen were analysed using an image visualization software. Statistical analysis of the obtained data was performed using the t-test. RESULTS: Measurements of the radii in the glenoid revealed a significantly larger radius for bone than cartilage, whereas for the humeral head the opposite was the case. Highest ratios for cartilage in the transverse plane were found in the inferior and central areas of the joint surface, whereas the smallest ratios were found in the superior area. The radial mismatch varied between 0.1 mm and 13.6 mm, depending on the measured plane. CONCLUSIONS: The results suggest that in abduction, the cartilaginous guidance of the humeral head decreases. This might permit the humeral head an anterior-posterior shifting as well as superior-inferior translation. Surgical reconstruction of the normal glenohumeral relationships necessitates precise information about the glenohumeral morphology to ensure proper sizing and correct placement of prosthetic components and osteochondral allografts

The Developing Regorafenib Eye drops for neovascular Age-related Macular degeneration (DREAM) study: an open-label phase II trial.

AIMS This program investigated topical regorafenib, a multikinase inhibitor, in patients with neovascular age-related macular degeneration (nAMD). METHODS Topical regorafenib was investigated in an open-label, phase IIa/b study in which patients with choroidal neovascularization (CNV) secondary to nAMD received regorafenib (25 μL, 30 mg/mL TID) for 12 weeks. The primary endpoint of the phase II/a/b study was mean change in best-corrected visual acuity (BCVA) from baseline to weeks 4 and 12. RESULTS In nAMD patients (N = 51), mean changes in BCVA were +1.2 (90% CI -0.61 to 2.97) and -2.4 (90% CI, -4.18 to -0.54) letters at weeks 4 and 12, respectively. Ocular treatment-emergent adverse events (TEAEs) (study eye) were reported in 21 patients by week 12. There was 1 serious ocular TEAE (visual acuity reduced) that was not drug related. Twenty patients required rescue (intravitreal ranibizumab). CONCLUSIONS The program was terminated after phase IIa ended because efficacy was less than with current nAMD treatments. According to elaborate post hoc analyses, the most likely reason was insufficient exposure in the target compartment (back of the eye)